Clinical History

Case one: a Caucasian 30-year-old man with no history of cardiovascular disease was admitted to our emergency department complaining of episodes of palpitation. The ECG showed supraventricular tachycardia.

Case two: a Caucasian 67-year-old woman with a recent right hemispheric ischaemic stroke and no history of diabetes, hypertension or smoking.

Imaging Findings

Case one: due to the exclusion of any other clear causes, case one underwent a cardiac 64-slice CT with retrospective cardiac ECG-gating, after the intravenous bolus injection of iodinated contrast agent. The examination showed a hypodense linear structure (Fig. 1) of 12 mm in extension (Fig. 2) situated in the left atrium, which connected the most caudal portion of the interatrial septum with the most caudal portion of the posterior wall of the left atrium. A small patent foramen ovale was also visible (Fig. 3).

Case two: in the suspicion of cardioembolic stroke, case two underwent a cardiac 64-slice CT with retrospective cardiac ECG-gating, after the intravenous bolus injection of iodinated contrast agent. It revealed a thin hypodense linear band (Fig. 4) of 16 mm in extension (Fig. 5) in a posterolateral left location between the interatrial septum and the posterior wall of the left atrium. No patent foramen ovale was evident.

Discussion

The presence of an anomalous muscular band has been found in the left ventricle, in the left and in the right atria [1]. Left atrial band (LAB) is a congenital cardiac anomaly with an incidence of 2% in autopsies studies [2].LAB is often associated with patent foramen ovale [3], mitral valve prolapse and mitral regurgitation [1, 4, 5]. Moreover, it increases the prevalence of premature atrial complex [3], and it might be also one of the causes of supraventricular arrhythmia [2]. However, the association with atrial fibrillation (AF) noticed by Katsunori et al. cannot be surely related to an AF-triggering premature complex arising from the band [3]. Therefore, it is so far not possible to demonstrate that the supraventricular tachycardia or the AF are generated by foci of electrical activity in the band. Furthermore, the presence of a left atrial band seemed to be connected with ischaemic stroke, particularly in the absence of a patent foramen ovale [5].The majority of LABs are linked with the left atrial side of the fossa ovalis endocardium and terminate in other areas within the left atrium. [1, 4]. They are made of fibrous and muscular tissues [4]. LABs can be associated with Chiari’s network, observed in 2% of the population, which is a reticulated network of fibres that arises from the Eustachian valve and connects several parts of the right atrium [2]. Left atrial band is easily detectable with a multidetector cardiac CT, which is widely available and well tolerated by the patients. Multiplanar CT images can be reconstructed in specific cardiac planes and maximum intensity projection and volumetric images may provide additional perspectives [6]. The treatment depends on symptoms: ablation could be suggested in presence of a significant arrhythmia, while an anticoagulant therapy is usually recommended in case of a previous stroke. The two cases are still under judgement.Although left atrial band is a rare anomaly, it must be considered in the diagnostic process of SVT and stroke. The differential diagnosis between left atrial band and other congenital entities, especially cor triatriatum, must be accurate.